Neuromedin U (NMU) is a neuropeptide with potent activity on smooth muscle which was isolated first from porcine spinal cord and later from other species. It is widely distributed in the gut and central nervous system. Peripheral activities of NMU include stimulation of smooth muscle, increase of blood pressure, alteration of ion transport in the gut, control of local blood flow, and regulation of adrenocortical function. Howard et al. (2000) demonstrated that the G protein-coupled receptors FM3 and FM4 are cognate receptors for NMU. FM3, which they designated NMU1R, is abundantly expressed in peripheral tissues, whereas FM4, which they designated NMU2R, is expressed in specific regions of the brain. NMU is expressed in the ventromedial hypothalamus in the rat brain, and its level is significantly reduced following fasting.